In galvanic cells, such as nonaqueous cells, the active cathode material in particulate form is generally mixed with a suitable binder and, if required, a conductive material and then deposited on a metal cathode collector to form a cathode electrode. In some cell systems, such as Li/MnO.sub.2 and Li/CF.sub.x systems, the metal cathode collector is subject to corrosion particularly at the cathode potential. Such corrosion has been associated with deterioration in the open circuit voltage of the cell and deterioration in the discharge performance of the cells after storage, particularly at elevated temperatures. This problem of cathode collector corrosion is particularly noticeable in coiled or jellyroll type cell constructions due to the large surface area of the cathode collector.
Japanese Patent Application No. 52-111625 discloses the use of cathode collectors made from metals such as nickel, stainless steel, titanium or aluminum, which have a surface coating of RuO.sub.2 formed by coating a Ru salt solution on the cathode collector and decomposing the salt to form a RuO.sub.2 layer. This RuO.sub.2 layer is stated as being corrosion resistant and conductive and therefore will serve as a protective coating for current collectors in cell systems such as lithium cell systems.
Japanese Patent Application No. 55-150557 discloses the use of an annealed metal substrate for thin cathode pellets to prevent cracking or distortion of the thin cathode pellets.
It is an object of the present invention to provide a cell employing among other components a cathode electrode composed of an active cathode material, preferably particulate, deposited on and/or in contact with a metal cathode collector and wherein the metal cathode collector has a protective layer of an oxide of the metal of said cathode collector to effectively prevent corrosion of the cathode collector during storage and discharge of the cell, particularly at the cathode potential.
Another object of the present invention is to provide a cathode electrode with a metal cathode collector, such as stainless steel, which has an oxide layer of the metal of the cathode collector on its surface to protect the cathode collector against corrosion when the electrode is assembled in a cell, such as a lithium cell.
Another object of the present invention is to provide a method for treating a metal cathode collector so that an oxide layer of the metal of the cathode collector is disposed on the surface of the cathode collector.
The foregoing and additional objects will become more fully apparent from the following description.